In studies of pituitary cell membrane signal transduction, we have looked for age-related changes in the levels of GTP regulatory units using specific antibodies against GalphaS, Galphai1&2, Galphai3, Galphaq, and beta-subunits. No significant changes due to age were found in the levels of GalphaS. Significant changes are seen in the levels of beta-subunit (35K) which predominates over the 36K (9:1). It is important to consider the levels of the beta-subunits since it is now clear that they regulate alpha-subunit activity without changes in alpha-subunit levels, activate K+ channels, and possibly have an effect, direct or indirect on Ca++ channels. There was a significant age-related decrease in levels of Galphai3, the GTP regulatory subunit that putatively inhibits adenylyl cyclase, and a significant increase in the levels of Galphaq which is involved in the activation of phospholipase C, the enzyme generating IP3 and diacylglycerol required for hormone release. In a new initiative on the effects of age on tissue responses to GH and testosterone in an animal model, we have cloned and successfully used labeled cDNA probes to quantify mRNA's for EF1-alpha in muscle and other tissues using Northern blotting and mRNA's for IGF-i and IGF-I receptor using the RNA'ase protection assay. Mice of ages 10 and 31 months have been treated daily for 5 or 10 days, killed, and tissues preserved. RNA extractions have been completed on muscle liver and kidney and quantification of specific mRNA's has begun. Total RNA (corrected for protein or tissue wet weight) and body weight were shown to increase in the treated mice, compared with age-matched placebo controls.